Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $112.46   11.320%   $125.1905   $125.19   $125.20   $125.20  
  Purchase #2 $167.96   4.731%   $175.9062   $175.91   $175.90   $175.90  
  Purchase #3 $232.57   13.359%   $263.639   $263.64   $263.65   $263.60  
  Purchase #4 $224.67   4.276%   $234.2769   $234.28   $234.30   $234.30  
  Purchase #5 $196.54   3.805%   $204.0183   $204.02   $204.00   $204.00  
  Purchase #6 $91.42   7.356%   $98.1449   $98.14   $98.15   $98.10  
  Purchase #7 $48.32   4.303%   $50.3992   $50.40   $50.40   $50.40  
  7 purchase totals = $1,073.94       $1,151.5750   $1,151.58   $1,151.60   $1,151.50